1. Field of the Invention
The present invention relates to a joined (or bonded, or cemented) optical member having a plurality of optical members (part optical members) joined together with adhesive, also relates to an image display apparatus incorporating such a joined optical member, and further relates to a head-mounted display (hereinafter also “HMD”) incorporating such an image display apparatus.
2. Description of Related Art
When two optical members are joined together with adhesive to form a joined optical member, the superfluous adhesive that oozes out from between the joined surfaces needs to be removed. This is achieved by, for example, the method disclosed in JP-A-H6-308349. According to this method, first the adhesive applied inside of the outer edges of the joined surfaces is hardened, and then the adhesive that has oozed outside of the outer edges of the joined surfaces is, still in its unhardened state, removed. Wiping off superfluous adhesive in its unhardened state in this way helps achieve easy and complete removal of the adhesive.
Wiping off adhesive in its unhardened state, however, results in more unhardened adhesive than needs to be wiped off being removed, leaving a recess along the joint seam (the border between the individual optical members joined together). This may degrade, for example, the optical performance with which an outside world image can be viewed through the joint seam.
On the other hand, for example, according to the method disclosed in JP-A-2006-195073, a coating layer is formed on the exterior surfaces of two optical members, then adhesive is hardened, and then the adhesive that has oozed outside of the coating layer is, in its hardened state, removed. Removing superfluous adhesive after hardening it in this way helps avoid removal of more adhesive than should be removed, and thus helps prevent degradation of the optical performance with which an outside world image can be viewed through the joint seam.
Inconveniently, however, with the method disclosed in JP-A-2006-195073 mentioned above, the coating layer is removed either after the superfluous adhesive is removed or at the same time that it is removed. This results in an unsatisfactory effect of preventing scratches on the exterior surfaces of the individual optical members. That is, when the superfluous adhesive is removed, the coating layer present between the exterior surfaces of the optical members and the adhesive offers a certain effect of preventing scratches on the exterior surfaces; in actual use of the joined optical member, however, since no coating layer is present on the exterior surfaces any longer, no effect of preventing scratches on the exterior surfaces is obtained. This may lead to degraded optical performance when those exterior surfaces are used as optical surfaces.